Here's what you do: it's important to get Senna-S and not plain Senna. Plain Senna is jut a laxative, but Senna-S is a combination of a Senokot which is a laxative, and the "S" portion is a stool softener called docusate which will help. If after 24 hours you don't see any relief, try getting one of those bottles of liquid magnesium citrate and pound the whole bottle (118 ml) follwed by 8 oz water. Try that or some Miralax. That should do the trick. But the magnesium citrate liquid should definitely help wonders along with the Senna-S.
If the Senna isn't doing it, try taking 10 mg of bisacodyl (brand name Dulcolax) along with docusate, and then drink the 118 ml of magnesium citrate. Some people who are undergoing colonoscopies are instructed to drink two 118 bottles of the magnesium citrate.
And also drink plenty of water; coffee and some nicotine can help too. And BrokedownPalace was right, don't take fiber or any type of bulking agents, this can make you situation worse and lead to an impacted bowel which will seriously fuck your day up.
And temporarily laying of the dope and going through mini WD is definintely a good idea to get your bowels moving. Won't be pleasant, but I'd take some minor WDs over an impacted bowel any day of the week.
Then there's always Taco Bell...